The present invention relates to a new work-up process for the preparation of a stabiliser mixture containing a low amount of chloride, which are suitable for stabilising organic materials against oxidative, thermal or light-induced degradation.
U.S. Pat. No. 4,075,163 discloses the synthesis of tetrakis(2,4-di-tert-butylphenyl)biphenylene diphosphonite (column 7, Table 1, compound 12) which is suitable for stabilising organic materials against oxidative, thermal or light-induced degradation. This compound is commercially available for example as Sandostab P-EPQ (RTM) from Clariant, Switzerland.
EP-A-0 633 287 discloses in Example 1 that this commercially available Sandostab P-EPQ (RTM) is a mixture of several components comprising a) 65% by weight of tetrakis(2,4-di-tert-butylphenyl)biphenylene diphosphonite, b) 15% by weight of bis(2,4-di-tert-butylphenyl)biphenylene monophosphonite, c) 13 parts by weight of tris(2,4-di-tert-butylphenyl) phosphite, d) 1.5 parts by weight of 2,4-di-tert-butyl phenol, e) up to 1% by weight of chloride [up to 10,000 mg/kg], f) up to 0.5% by weight of volatiles, and g) 4-5% by weight of the oxidised tetrakis(2,4-di-tert-butylphenyl)biphenylene diphosphonite.
Phosphites and phosphonites are hydrolytically very labile (see Example 29 in U.S. Pat. No. 4,075,163). Therefore, during the synthesis of Sandostab P-EPQ (RTM) the reaction mixture was never brought into contact with water. In the actual large scale production of Sandostab P-EPQ (RTM) the neutralisation of the remaining aluminium trichloride/pyridine/hydrochloric acid complex is done with gaseous ammonia (see comparative Example 2 in the instant application). However, some of the formed salts like for example ammonium chloride remain in the final product. These salt impurities may be the reason why the final stabiliser mixture is slightly turbid. A turbid stabiliser for polyolefins, however, induces some haze in polyolefins which is for some applications clearly undesired.
The goal of the instant invention was therefore to find an improved work-up process for the synthesis of Sandostab P-EPQ (RTM) containing a low amount of chloride and forming a product which is not turbid and does not induce any haze into synthetic polymers.
The present invention therefore relates to a process for the preparation of a stabiliser mixture containing a low amount of chloride comprising
a) 50-80% by weight of a diphosphonite of the formula I 
b) 5-25% by weight of a monophosphonite of the formula II 
c) 5-25% by weight of a phosphite of the formula III 
in which R is a radical of the formula IV 
and where the sum of the compounds of the formula I, II and III is not greater than 100% by weight,
by reacting a biphenyl of the formula V 
under Friedel-Crafts condition with phosphorus trichloride and aluminium trichloride and by reacting the product mixture with 2,4-di-tert-butyl-phenol of the formula VI 
in the presence of a tertiary amine or an aromatic amine and a solvent, separating the formed two layers, which process comprises treating the solvent layer with water, a base and a desiccant, separating the precipitate from the solution containing the stabiliser mixture and evaporating the solvent.
A preferred tertiary amine is a compound of the formula VII 
wherein R1, R2 and R3 are the same or different, and are C1-C24alkyl; C4-C24alkyl interrupted by one or more O-atoms; phenyl, C7-C9phenylalkyl; C7-C9alkylphenyl; or two of R1, R2 and R3 together with the N-atom to which they are attached form a 5-, 6- or 7-membered heterocyclic residue, which optionally contains further oxygen, nitrogen or sulphur atom and which is optionally substituted by one or more C1-C4alkyl groups, and the other of R1, R2 and R3 is C1-C24alkyl or C4-C24alkyl interrupted by one or more O-atoms.
Alkyl having up to 24 carbon atoms is a branched or unbranched radical, for example methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, 2-ethylbutyl, n-pentyl, isopentyl, 1-methylpentyl, 1,3-dimethylbutyl, n-hexyl, 1-methylhexyl, n-heptyl, isoheptyl, 1,1,3,3-tetramethylbutyl, 1-methylheptyl, 3-methylheptyl, n-octyl, 2-ethylhexyl, 1,1,3-trimethylhexyl, 1,1,3,3-tetramethylpentyl, nonyl, decyl, undecyl, 1-methylundecyl, dodecyl, 1,1,3,3,5,5-hexamethylhexyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, icosyl or docosyl. One of the preferred definitions for R1, R2 and R3 is, for example, C2-C18alkyl. An especially preferred definition for R1, R2 and R3 is C2-C8alkyl, for example ethyl.
C4-C24alkyl interrupted by one or more O-atoms include, e.g. 2-ethoxypropyl, 1-methoxypropyl, 1-methoxybutyl, n-butoxyethyl, 1-methoxyoctyl, 1-methoxydecyl, 1-methoxydodecyl, 1-methoxyhexadecyl, 1-methoxyeicosyl, 1-methoxytetraeicosyl and 2-methoxyethoxymethyl.
C7-C9Phenylalkyl is, for example, benzyl, xcex1-methylbenzyl, xcex1,xcex1-dimethylbenzyl or 2-phenylethyl. Preference is given to benzyl.
Heterocyclic groups formed by two of R1, R2 and R3 are preferably 6-membered, examples of which are piperidino, morpholino, thiomorpholino and 4-C1-C4alkyl-piperazino.
A preferred aromatic amine is pyridine which is optionally substituted by one or more C1-C4-alkyl groups.
Pyridine which is optionally substituted by one or more C1-C4alkyl group is, for example, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine or 3,4-lutidine.
A preferred solvent is benzene which is optionally substituted by one or more chlorine or C1-C4alkyl groups.
Benzene which is optionally substituted by one or more chlorine or C1-C4alkyl groups is, for example, chlorobenzene, toluene or xylene. Preferred is chlorobenzene.
A preferred base is an alkaline metal- or an alkaline earth metal-hydroxide, oxide, hydrogen phosphate, dihydrogen phosphate, carbonate, hydrogen carbonate or tetraborate.
An alkaline metal- or alkaline earth metal-hydroxide, oxide, hydrogen phosphate, dihydrogen phosphate, carbonate, hydrogen carbonate or tetraborate is, for example, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, calcium oxide, sodium hydrogen phosphate, sodium dihydrogen phosphate, sodium carbonate, calcium carbonate, sodium hydrogen carbonate or sodium tetraborate decahydrate.
Advantageously, the base is used in an amount of from 0.1 to 10% by weight, especially from 0.1 to 5% by weight, e.g. from 0.1 to 2% by weight, based on the weight of the solvent layer.
A preferred desiccant is an alkaline metal sulfate, an alkaline earth metal sulfate or oxide, a molecular sieve or aluminium oxide.
An alkaline metal sulfate, an alkaline earth metal sulfate or oxide, a molecular sieve or aluminium oxide is, for example, magnesium oxide, calcium oxide, sodium sulfate, magnesium sulfate, barium sulfate, molecular sieve 3 xc3x85, molecular sieve 4 xc3x85, powdered aluminium oxide, basic aluminium oxide, calcined aluminium oxide, fused aluminium oxide, fused aluminium oxide, granulated aluminium oxide or sintered aluminium oxide.
Advantageously, the dessicant is used in an amount of from 0.1 to 10% by weight, especially from 0.1 to 5% by weight, e.g. from 0.1 to 2% by weight, based on the weight of the solvent layer.
Some dessicants like for example sodium sulfate can also act as a cation precipitant.
Of interest is a process for the preparation of a stabiliser mixture containing a low amount of chloride, which comprises treating the solvent layer additionally with a filter-aid before separating the precipitate from the solution containing the stabiliser mixture.
A preferred filter-aid is, for example, fuller""s earth [Merck Index 10th Edition, 4162 (1983)] or infusorial earth [Merck Index 10th Edition, 4857 (1983)] which includes floridin, a nonplastic variety of kaolin containing an aluminium magnesium silicate, kieselgur, celite, diatomaceous earth like for example Hyflo Super Cel [(RTM), Aldrich 39,254-5].
Advantageously, the filter-aid is used in an amount of from 0.1 to 10% by weight, especially from 0.1 to 5% by weight, e.g. from 0.1 to 2% by weight, based on the weight of the solvent layer.
Of special interest is a process for the preparation of a stabiliser mixture containing a low amount of chloride, which comprises that the water is added in the form of crystalline water which is present in the base.
A preferred base with crystalline water is, for example, sodium tetraborate decahydrate (Na2B4O7 10 H2O), Na2HPO4 12 H2O or Na2CO3 10 H2O.
Preferred is a process for the preparation of a stabiliser mixture containing a low amount of chloride, which comprises treating the solvent layer with water, a base and a desiccant at a temperature range of 0-25xc2x0 C., for example 5-20xc2x0 C.
Preferred is also a process for the preparation of a stabiliser mixture containing a low amount of chloride, which comprises treating the solvent layer with water, a base and a desiccant so that the pH range is of from 7.0 to 13, especially of from 7.5 to 12, e.g. of from 8 to 12.
Of special interest is a process for the preparation of a stabiliser mixture containing a low amount of chloride, which comprises treating the solvent layer with water in an amount of from 0.1 to 10% by weight, especially from 0.1 to 5% by weight, e.g. 0.1 to 2% by weight, based on the weight of the solvent layer.
Of special interest is also a process for the preparation of a stabiliser mixture in which the amount of chloride in the final product mixture is lower than 5,000 mg/kg, especially lower than 1500 mg/kg, e.g. lower than 500 mg/kg.
In the reaction of biphenyl of the formula V under Friedel-Crafts condition with phosphorus trichloride and aluminium trichloride, the phosphorus trichloride is preferably used as reagent and solvent. Thus, for the reaction of one mole biphenyl, 3 to 10 mole, especially 3 to 8 mole, e.g. 3 to 5 mole, of phosphorus trichloride is used. Preferably the reaction is kept under reflux for 4 to 10 hours, especially 4 to 8 hours, e.g. 5 to 7 hours. Preferably, the excess phosphorus trichloride is distilled off. In the subsequent reaction of the crude product mixture with 2,4-di-tert-butyl-phenol in the presence of a tertiary amine or an aromatic amine and a solvent the temperature range is advantageously of from 10 to 100xc2x0 C., especially from 10 to 80xc2x0 C., e.g. from 20 to 80xc2x0 C. The concentration of the reaction mixture is advantageously of from 10 to 80% by weight, especially from 10 to 60% by weight. The tertiary amine or the aromatic amine is used advantageously in a molar excess of from 10 to 100%, especially from 20 to 80%, e.g. from 30 to 70% based on the molar amount of 2,4-di-tert-butyl-phenol.
This improved Sandostab P-EPQ (RTM) is named in the further paragraphs LCT (Low-Chloride-Transparent) stabiliser mixture. This LCT stabiliser mixture is suitable for stabilising organic materials against oxidative, thermal or light-induced degradation.